• The Journal of Korean Academy of Prosthodontics
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• v.59 no.3
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• pp.370-378
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• 2021

Purpose. The purpose of this study was to evaluate the currently published literatures investigating the accuracy of computer-aided design and computer-aided manufacturing removable partial denture (CAD-CAM RPD) framework with different manufacturing techniques and methods. Materials and methods. A comprehensive search for literatures was conducted in PubMed database using specific keywords with the patient, intervention, comparison, and outcome (PICO) question, "Is there a difference in accuracy of RPD frameworks manufactured using digital workflow according to the manufacturing process and methods?" Results. A total of 7 articles were selected. Two studies compared intraoral scanning and laboratory scanning for RPD frameworks and had heterogenous results. In the studies using different manufacturing process, RPD frameworks had clinically acceptable accuracy in both subtractive and additive manufacturing. Polyetheretherketone (PEEK)-milled RPD frameworks showed higher fit accuracy than traditionally casted or 3D printed RPDs. Direct milling method showed a higher accuracy than indirect milling method. However, in rapid prototyping, indirect method showed higher accuracy than direct method. Conclusion. The RPD frameworks fabricated using CAD-CAM technology showed a clinically acceptable level of accuracy regardless of manufacturing process or techniques. Consistent results have not been reported regarding the digital impression methods, which were intra oral scanning or laboratory scanning, and further studies are needed.

• Journal of Electrochemical Science and Technology
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• v.15 no.2
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• pp.299-313
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• 2024

Electrochemical machining (ECM) is an effective manufacturing method for difficult-to-machine materials and is widely used in the precision manufacturing of aerospace components. In recent years, the requirements for the machining accuracy and surface integrity of ECM have become increasingly stringent. To further improve the machining quality, this work investigated the intricate laws between electrolyte filtration accuracy and machining quality. Electrolytes with different filtration accuracies were compared, and a numerical simulation was used to evaluate the change in temperature and bubble rate of the flow field in the machining area. Experiments were conducted on ECM of Ti-6Al-4V (TC4) alloy workpieces using electrolytes with different filtration accuracy. The workpiece machining accuracy and surface quality were analyzed, and the repetition accuracy of the workpiece was evaluated. The intricate laws between electrolyte filtration accuracy and machining quality were explored. It was found that when the electrolyte filtration accuracy is improved, so too is the machining quality of the ECM. However, once the filtration accuracy has reached a certain value, the machining quality has extremely limited improvement. By evaluating the repetition accuracy of processed workpieces in electrolytes with different filtration accuracies, it was found that when the filtration accuracy reaches a certain value, there is no positive correlation between the repetition accuracy and filtration accuracy. The result shows that, for the workpiece material and conditions considered in this paper, an electrolyte with 0.5㎛ filtration accuracy is suitable for the wide application of precision ECM.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.12 no.2
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• pp.121-126
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• 2013

Precision machine tools for high dignity cutting are needed for efforts to improve machining accuracy. However, there are many factors to improve machining accuracy. This study investigated how machining accuracy changes when variation and unbalance amount in rotational speed domain is decreased. Machining accuracy of initial machine tools depends on manufacturing and assembly of parts such as bearing. And then, vibration and noise vary with volume of unbalance amount when it is rotation, so it effects unbalance amount. Also vibration and noise increased by unbalance shorten spindle's life and it especially makes worse boring accuracy. Therefore, this study studied the change of roundness and cylindricity of workpiece when it decreases variation and unbalance in rotational speed domain.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.1047-1050
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• 1997

Rapid Prototyping(RP) is an efficient method for rapid design verification and trial manufacturing. In order to improve their unique characteristics according to the working principles. Variable Lamination Manufacturing process and corresponding CAD/CAM system is developed. The objective of this study is to improve dimensional accuracy of VLM-ST process, and it can be done by offset for cutting error correction, cutting path correction for sharp edge and reference shape generation. To verify the proposed algorithms, they applied to three-dimensional shapes, such as spanner and mechanical part.

• Korean Journal of Computational Design and Engineering
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• v.8 no.4
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• pp.212-221
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• 2003

In order to reduce the lead-time and cost, the technology of rapid prototyping (RP) has been widely used. A new rapid prototyping process, transfer-type variable lamination manufacturing process by using expandable polystyrene foam (VLM-ST), has been developed to reduce building time, apparatus cost and additional post-processing. At the same time, VLM Slicer, the CAD/CAM software for VLM-ST has been developed. In this study, algorithms for accuracy improvement of VLM-ST, which include offset and overrun of a cutting path and generation of a reference shape are developed. Offset algorithm improves cutting accuracy, overrun algorithm enables the VLM-ST process to make a shape of sharp edge and reference shape generation algorithm adds additional shape which makes off-line lamination easier. In addition, proposed algorithms are applied to practical CAD models for verification.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.21-26
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• 2004

This research presents a modeling and a manufacturing method of insert type milling cutters such as face cutter, flat endmill and ball endmill. The methods introduced in this paper adopts the multi-tasking 5-axis machining that is increasing machining accuracy of holder and position accuracy of bolting points. So this can be used in the basic document of the total package program that involves modeling and manufacturing module in various insert cutters.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.4
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• pp.33-39
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• 2010

Manufacturing accuracy of a precision instrument was essential to stability and efficiency of the product. Accordingly, geometrically accuracy management of precision instrument was very becoming the technique in order to design and manufacturing for machine. In this study, Measuring System is developed for extra long roller using non-contact sensor. Futhermore, It's studied by Geometric Tolerance. Exact roundness is obtained to Least Squares method from the reference circle of measured data. Measuring System is analyzed point of measurement and straightness of extra long roller is evaluated by FEM.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.187-195
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• 2006

FDM, SLS, and EOS processes are the layered manufacturing processes far functional prototypes. In this paper, bench mark tests of those processes were carried out using various materials. The test includes mechanical properties, such as tensile and compressive strengths, hardness, impact strength, and heat resistance, and surface roughness, shape and dimensional accuracy, manufacturing time, and manufacturing costs. It is verified that SLS method is advantageous in surface roughness and manufacturing time, EOS method in shape accuracy, and FDM method is great in manufacturing costs.

• International Journal of Precision Engineering and Manufacturing
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• v.4 no.4
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• pp.57-63
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• 2003

Machining information such as form accuracy and surface roughness is an important factor for manufacturing precise parts. To this regard, OMM (On the Machine Measurement) has been researched for last several decades to alternate CMM (Coordinate Measurement Machine) process. In this research, the OMM system with a laser displacement sensor was developed for measuring form accuracy and surface roughness of the machined workpiece on the machine tool. The surface roughness was estimated comparing the sensory signal with the reference data measured from master specimen. Also, form accuracy was determined from the moving averaged raw data. In addition, the geometric error map constructed beforehand using the geometric errors of the machine tool was used to compensate the obtained form accuracy. The overall performance was compared with CMM result, and verified the feasibility of the measurement system.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.38-45
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• 2016

Since a 5-axis machine tool has two rotary axes, it offers numerous advantages, such as flexible accessibility, longer tool life, better surface finish, and more accuracy. Moreover, it can conduct whole machining by rotating the rotary feed axes while setting the fixture at once without re-fixing in contrast to conventional 3-axis machining. However, it is difficult to produce complicated products that have a hollow shape. In contrast, 3D printing can produce an object with a complicated hollow shape easily and rapidly. However, because of layer thickness and shrinkage, its surface finish and dimensional accuracy are not adequate. Therefore, this study proposes hybrid technology by integrating the advantages of these two manufacturing processes. 3D printing was used as the additive manufacturing rapidly in the whole body, and 5-axis machining was used as the subtractive manufacturing accurately in the joining and driving places. The reliability of the proposed technology was verified through a comparison with conventional technology in the aspects of processing time, surface roughness. and dimensional accuracy.